The present invention relates to liquid delivery systems. The invention is particularly useful as an implantable micro-pump for delivering insulin or other drugs, and is therefore described with respect to such application, but it will be appreciated that the invention, or various aspects of it, could advantageously be used in other applications as well.
A number of liquid delivery systems or micro-pumps have been devised and are described in the literature, but the known ones suffer from a number of drawbacks, particularly when used as an implantable unit for delivering insulin or other drugs to the human body. Thus, in some of the known systems, there is a rapid deterioration of the insulin or other drug being delivered because of a number of factors including incompatability with the material of the container or other elements of the system with which the feed liquid comes into contact, and/or shear forces applied to the liquid arising from opening and closing of valves, turbulent flow, and the like. Another difficulty is the danger of overdosage or overfilling of the feed liquid or other drug reservoir during refilling, which can result in serious bodily harm or even death. Further difficulties are the requirements for high accuracy in the dosage, and the prevention of air bubbles, which are very hard to fulfill in the known pumping systems, particularly the non-self-priming pumps.